I've just tried to add a texture to a plane in P3D4. The system refused my entry into the cfg file, I tried a different plane, and the same thing happened. I'd appreciate guidance on how to do a simple texture-add in P3D4. Thanks!

I've just tried to add a texture to a plane in P3D4. The system refused my entry into the cfg file, I tried a different plane, and the same thing happened. I'd appreciate guidance on how to do a simple texture-add in P3D4. Thanks!

Which aircraft?
What is the path to the file?
What is the full (refused) message you get?